Studies of job activity and colon cancer suggest a decreased risk associated with high activity jobs. In addition, there has been a decline in colon cancer incidence among men and women under age 50 in western Washington, which may be related to an increase in leisure time activity. The specific aims of this study are: (1) to determine if physical activity (job activity plus leisure activity) is related to a reduced risk of colon cancer, and (2) to determine whether leisure time activity affects colon cancer incidence independently of job related physical activity. While the first aim addresses an etiologic question, the second will help answer the cancer control issue of whether an exercise program during leisure time could be an intervention to prevent colon cancer. To study the relationship between physical activity and colon cancer, we propose a population based case-control study of 400 cases and 400 controls. The case group will be incident colon cancer cases age 25-59 diagnosed between January 1986 and December 1990 in three counties in western Washington State identified through the Seattle-Puget Sound SEER Cancer Registry. Controls will be an age and sex stratified sample identified through random digit dialing. Cases and controls will be interviewed by telephone. Questions will concern leisure time physical activity, job activity, household activity, diet, weight, and demographic characteristics. Data analysis will focus on the effect of physical activity on colon cancer, using quantitative estimates of energy expenditure categorized by type of activity (e.g., leisure activities) and by intensity of activity. Various components of diet including calories, fat, fiber, calcium and vitamin A will also be considered in the analyses.